Changeset 6e16301 for lib

Timestamp:

11/01/17 10:24:26 (3 years ago)

Author:

Shane Alcock <salcock@…>

Branches:

cachetimestamps, develop, dpdk-ndag, etsilive, master, ndag_format, rc-4.0.2, rc-4.0.3, rc-4.0.4, ringdecrementfix, ringperformance

Children:

8fa0167

Parents:

ea75ec2

Message:

Try to avoid selecting() if all socket buffers have data available.

File:

• lib/format_ndag.c (modified) (4 diffs)

lib/format_ndag.c

@@ -638 +638 @@
 
         fd_set allgroups;
-        int maxfd, i, ret, readybufs;
+        int maxfd, i, ret, readybufs, availsocks;
         struct timeval timeout;
 
-        FD_ZERO(&allgroups);
         maxfd = 0;
         timeout.tv_sec = 0;
@@ -650 +649 @@
          * port.
          */
+
+        readybufs = 0;
+        availsocks = 0;
 
         for (i = 0; i < rt->sourcecount; i ++) {
@@ -657 +659 @@
                                 maxfd = rt->sources[i].sock;
                         }
-                }
-        }
-
+                        availsocks += 1;
+                } else if (rt->sources[i].sock != -1) {
+                        readybufs += 1;
+                        availsocks += 1;
+                }
+        }
+
+        /* If all of our sockets already have data sitting in their
+         * buffers then we can save ourselves some 'select'ing.
+         */
+        if (availsocks == readybufs) {
+                return readybufs;
+        }
+
+        /* Otherwise, at least one active socket has an empty buffer so
+         * we better try to read some data from those sockets (just in
+         * case the correct 'next' packet is waiting on one of those
+         * sockets.
+         */
+        FD_ZERO(&allgroups);
         if (select(maxfd + 1, &allgroups, NULL, NULL, &timeout) < 0) {
                 fprintf(stderr, "Error waiting to receive records: %s\n",
@@ -666 +685 @@
         }
 
-        readybufs = 0;
 
         for (i = 0; i < rt->sourcecount; i ++) {